The present invention relates generally to a new engine for use in, for example, personal watercraft. In particular, the present invention relates to a new four-stroke in-line engine that was developed with a view to the future stricter environmental and emission regulations. The engine has a supercharger for enhancing engine performance.
There is a very popular type of watercraft known as a xe2x80x9cpersonal watercraftxe2x80x9d which is designed to be operated primarily by a single rider. Although this type of watercraft is commonly employed for single riders, frequently provisions are made for accommodating additional passengers although the maximum number of passengers is more limited than conventional types of watercraft.
This type of watercraft is also generally quite sporting in nature and normally accommodates at least the rider on a type of seat in which the rider sits in a straddle fashion. The passenger""s area is frequently open through the rear of the watercraft so as to facilitate entry and exit of the rider and passengers to the body of water in which the watercraft is operating, as this type of watercraft is normally ridden with passengers that are wearing swimming suits.
These personal watercraft are generally quite small so that they can be conveniently transported from the owner""s home to a body of water for its use. Because of the small size, the layout of the components is extremely critical, and this gives rise to several design considerations that are peculiar to this type of watercraft. However, due to its sporting nature it is also desirable if the watercraft is powered by an engine and propulsion device that are not only efficient but also generate sufficient power.
Traditionally, two-cycle engines have been used to power watercraft, including personal watercraft. These engines have the advantage that they are fairly powerful, relatively lightweight, and compact.
One particular disadvantage to the two-cycle engine is its emission content. Two-cycle engines generally exhaust larger quantities of hydrocarbons and other pollutants than four-cycle engines due to cylinder charging inefficiencies and the combustion of lubricating oil among other things. When measures are taken to reduce emissions of the two-cycle engine, other generally undesirable consequences can result, such as an increase in the weight of the engine, a reduction of its power output or the like. With concern for the environment and increasingly strict emissions requirements being instituted by various governing bodies. There is motivation to provide a power plant that reduces exhaust emissions while retaining other advantageous characteristics such as compactness, low weight and high power output.
Four-cycle engines are commonly used as power plants in other applications, such as automobiles. These engines have the advantage that their emissions output are generally desirably lower as compared to a two-cycle engine for a given power output. These engines are typically larger than two-cycle engines and present numerous spatial issues when located in a personal watercraft.
Superchargers are used to enhance engine performance. To date, the present inventors are not aware of the use of a supercharger in an engine for a personal watercraft. U.S. Pat. No. 5,634,422 to Kobayashi et al., entitled xe2x80x9cPersonal Watercraft With V-Type Engine,xe2x80x9d U.S. Pat. No. 5,647,779 to Nanami, entitled xe2x80x9cManifold and Water Trap System For A Marine Engine,xe2x80x9d U.S. Pat. No. 5,839,930 to Nanami et al., entitled xe2x80x9cEngine Lubricating System For Watercraft,xe2x80x9d and U.S. Pat. No. 5,846,102 to Nitta et al., entitled xe2x80x9cFour-Cycle Engine For A Small Jet Boatxe2x80x9d disclose various engines for personal watercraft. None of these references disclose the use of a supercharger.
It is an object of the present invention to provide a four stroke, in-line engine having a compact construction.
It is another object of the present invention to provide a four stroke, in-line engine having a modular construction to permit the interchange of parts between various engine models.
It is another object of the present invention to provide a four stroke, in-line engine having improved exhaust emission characteristics.
It is another object of the present invention to provide a four stroke engine having a narrow and low profile.
It is another object of the present invention to provide a four stroke engine having a low profile valve actuation assembly for controlling the operation of the intake and exhaust valves.
It is another object of the present invention to provide a cylinder head having a low profile to reduce engine height.
It is another object of the present invention to offset the placement-of the intake valves and exhaust valves with respect to a vertical axis within the cylinder head to reduce engine height.
It is another object of the present invention to provide an improved spark plug mounting assembly for easy access within the cylinder head.
It is another object of the present invention to provide a Y-shaped intake rocker arm assembly providing compact construction.
It is yet another object of the present invention to provide a four stroke engine having an improved oil collection system and oil holding tank.
It is another object to provide a four stroke engine which combines a closed loop cooling system and an open loop cooling system for enhanced cooling of the engine in accordance with the present invention.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open loop cooling system enhances cooling of the crankcase and cylinder head.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open cooling system lowers the temperature of the exhaust manifold such that the exhaust manifold functions as a heat sink for the crankcase and cylinder head.
It is another object of the present invention to provide a closed loop cooling system for selectively cooling the crankcase and cylinder head of the four stroke engine.
It is another object of the present invention to provide a closed loop cooling system having a selectively operable heat exchanger.
It is another object of the present invention to provide a supercharger for enhanced engine performance.
The present invention is directed to a supercharged four stroke internal combustion engine. The supercharged engine includes a crankcase having a crankshaft rotatably mounted therein and a cylinder head connected to the crankcase. The crankcase and the cylinder head form at least three combustion cylinder. Each cylinder includes at least one intake valve and at least one exhaust valve. A valve actuation assembly operates the intake and exhaust valves. An air intake passageway is operatively coupled to the cylinders through the intake valves. An air intake manifold is connected to the cylinder head and operatively connected to the air intake passageways. A power take off housing is located on one end of the crankcase. The crankshaft terminates within the power take off housing. The engine includes a supercharger for boosting air intake to the air intake manifold. The supercharger is mounted to the power take off and operatively connected to the crank shaft within the power take off housing.
In accordance with the present invention, the air intake manifold is preferably formed from a plastic material and includes a central air passageway. The central air passageway is operatively connected to the supercharger. The air intake manifold further includes a flame arrester located within the central air passageway. The flow of air from the supercharger travels through the central air passageway and the flame arrester.
In accordance with the present invention, the supercharger includes a mounting portion. The mounting portion is positioned within a mounting opening in the power take off housing. The supercharger further includes an inlet portion having an inlet opening. The inlet portion is connected to the mounting portion. An air passageway extends from the inlet opening to the air intake manifold.
The supercharger further includes a blower located within the inlet portion for directing a stream of air to the air intake manifold. The blower includes a blower drive shaft, which is rotatably mounted within the mounting portion. The blower drive shaft is operatively connected to the crank shaft through a connection assembly.
The connection assembly dampens the transmission of vibrational from the crankshaft to the blower drive shaft. The connection assembly includes a blower drive pinion located on one end of the blower drive shaft and a biased intermediate member located on the one end of the blower drive shaft. The biased intermediate member applies a force on the blower drive pinion such that the blower drive pinion is engaged with a rotating member secured to the crankshaft.
The rotating member includes a plurality of rotating gears. One of the rotating gears engages the blower drive pinion. Another rotating gear engages an engine starting mechanism. One of the rotating gears drives a balance shaft located within the crankcase.
The present invention is also directed to a personal watercraft. The personal watercraft includes a hull, a seating assembly, and a four stroke internal combustion engine secured to the hull below the seating assembly. The engine includes a supercharger for boosting air intake to the air intake manifold. The supercharger is located at one end of the crankcase.